Calculate the change in structural efficiency for both bending stiffness and strength when a solid flat panel of unit area and thickness \(t\) is foamed to give a foam panel of unit area and thickness \(h\), at constant mass. The modulus \(E\) and strength \(\sigma_{f}\) of foams scale with relative density \(ho / ho_{s}\) as

\[E=\left(\frac{ho}{ho_{s}}\right)^{2} E_{s} \quad \text { and } \quad \sigma_{f}=\left(\frac{ho}{ho_{s}}\right)^{3 / 2} \sigma_{f s}\]

where \(E,{ }^{\sigma_{f}}\) and \(ho\) are the modulus, strength and density of the foam and \(E_{s}, \sigma_{f, s}\) and \(ho_{s}\) those of the solid panel.